package demo3;

import java.util.TreeSet;
@SuppressWarnings({"all"})
public class Test {
    public static void main(String[] args) {
        TreeSet set = new TreeSet();
        set.add(new Person());
        set.add(new Person());
        set.add(new Person());
        System.out.println(set);
    }
}

class Person implements Comparable{
    @Override
    public int compareTo(Object o) {
        return 0;
    }
}
